VOX—[5 MAY 2016] On Thursday, many Americans are celebrating a holiday they likely know almost nothing about.

I’m speaking, of course, of Cinco de Mayo, which is Spanish for May 5. Although the day is supposed to celebrate Mexican heritage, it has become Americanized — that is, hijacked into another excuse to party, eat, and drink, all while getting sweet discounts at some restaurants. (It is so Americanized, in fact, that it’s actually celebrated more in the US than in Mexico.)

The origins of the holiday go back to, as one would expect, Mexican history. But Cinco de Mayo is not Mexican Independence Day (September 16), as many people believe. It is, instead, a day commemorating an important battle after Mexican independence.

These details might not seem very important. But the origins are an important part of the Mexican heritage many Americans are supposed to be celebrating today — and give some insight into why this uniquely Mexican-American holiday is now celebrated in the US.

Let’s be clear: Mexican Independence Day is September 16, 1810, the beginning of Mexico’s revolt against Spain. It is not Cinco de Mayo.